Title

Author

Date of Award

12-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Electrical Engineering

Advisor

Collins, Edward R

Committee Member

Groff , Richard E

Committee Member

Bridgwood , Michael A

Abstract

In recent years, the proliferation of single phase power electronics based loads has given rise to a number of power quality issues in the power grid. Harmonics in voltage and current waveforms are one of the biggest problems in this family of power quality issues. Until some years back, power system utilities did not consider harmonics due to small single phase loads to be a big problem. In fact, only large loads were considered as potential hotspots for power quality problems. However, the advent of compact fluorescent lamps (CFLs), personal computers and consumer electronic devices, which utilize rectifier front ends, have changed the scenario drastically. All these devices are rich sources of harmonics and their sheer volume makes them a serious power quality hazard. Recent work done by the Clemson University Power Quality and Industrial Applications (PQIA) lab has shown that capacitor run single phase induction motors also exacerbate the problem because of their behavior in the presence of harmonic infested voltage. This thesis attempts to study the behavior of capacitor run single phase induction motors in the presence of voltage harmonics. It incorporates laboratory results which show that the capacitor start capacitor run single phase motor actually `amplifies' the amount of harmonic distortion present in the source because of harmonic resonance in its auxiliary winding. This resonance behavior implies that machine impedance is a function of supply frequency and that the impedance hits a low value at the resonant frequency of the auxiliary winding circuit. This resonance leads to extra heating losses in the auxiliary winding circuit. However, during the course of investigation, an interesting phenomenon was observed. In the presence of single phase full wave rectifiers, this resonance phenomenon causes the single phase motor to behave as a harmonic filter. This harmonic filter helps `clean up' the voltage source by reducing the amount of harmonic current drawn by the motor-rectifier combination. Thus, resonance in the auxiliary winding of the single phase induction motor is not necessarily an unwanted phenomenon. This thesis presents experimental proof for all the phenomena outlined and makes an attempt to explain them. Arguments have then been presented for and against this peculiar behavior of the motor. Finally, the thesis concludes by outlining the scope for future work and the particular direction in which the power industry is headed with regards to single phase induction motors.